Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to a top emission type transparent organic light emitting display device and a method of manufacturing the same.
Discussion of the Related Art
Organic light emitting display devices are self-emitting devices and have low power consumption, a fast response time, high emission efficiency, high luminance, and a wide viewing angle. The organic light emitting display devices are classified into a top emission type and a bottom emission type, based on a transmission direction of light emitted from an organic light emitting device. In the bottom emission type, a circuit element is disposed between an emission layer and an image displaying surface, and for this reason, an aperture ratio is lowered. On the other hand, in the top emission type, the circuit element is not disposed between the emission layer and the image displaying surface, and thus, an aperture ratio is enhanced.
FIG. 1 is a schematic cross-sectional view of a related art top emission type organic light emitting display device. As illustrated in FIG. 1, a thin film transistor (TFT) layer T, a passivation layer 20, a first planarization layer 31, a second planarization layer 32, a first anode electrode 40, a second anode electrode 60, a first auxiliary electrode 50, a second auxiliary electrode 70, a bank 80, a partition wall 92, an organic emission layer 94, and a cathode electrode 96 may be formed in an active area AA on the substrate 10.
The TFT layer T includes an active layer 11, a gate insulation layer 12, a gate electrode 13, an interlayer dielectric 14, a source electrode 15, and a drain electrode 16. The first anode electrode 40 and the first auxiliary electrode 50 are formed on the first planarization layer 31, and the second anode electrode 60 and the second auxiliary electrode 70 are formed on the second planarization layer 32. The first auxiliary electrode 50 reduces a resistance of the cathode electrode 96 along with the second auxiliary electrode 70.
The bank 80 is formed on the second anode electrode 60 and the second auxiliary electrode 70 to define a pixel area, and the organic emission layer 94 is formed in the pixel area defined by the bank 80. The cathode electrode 96 is formed on the organic emission layer 94.
The partition wall 92 is formed on the second auxiliary electrode 70. The partition wall 92 is spaced apart from the bank 80 by a certain distance, and the second auxiliary electrode 70 and the cathode electrode 96 are connected to each other through a separation space between the partition wall 92 and the bank 80 to reduce a resistance of the cathode electrode 96.
In the top emission type, a light emitted from the organic emission layer 94 is released through the cathode electrode 96. Therefore, the cathode electrode 96 is formed of a transparent conductive material, and for this reason, a resistance of the cathode electrode 96 is high. In order to decrease the resistance of the cathode electrode 96, the cathode electrode 96 is connected to the first auxiliary electrode 50 and the second auxiliary electrode 70.
Particularly, in the related art organic light emitting display device illustrated in FIG. 1, two auxiliary electrodes (e.g., the first auxiliary electrode 50 and the second auxiliary electrode 70) connected to each other are formed for reducing the resistance of the cathode electrode 96. In this case, the second auxiliary electrode 70 is formed on the same layer as the second anode electrode 60, and thus, if a width of the second auxiliary electrode 70 is enlarged to reduce the resistance of the cathode electrode 96, a width of the second anode electrode 60 should be reduced. In this case, the pixel area of the display device is reduced, and for this reason, there is a limitation in the amount that the width of the second auxiliary electrode 70 may be enlarged. Therefore, in the related art, in order to solve the problems, the first auxiliary electrode 50 is additionally formed under the second auxiliary electrode 70, thereby reducing the resistance of the cathode electrode 96 without any reduction in pixel area.
The related art top emission type organic light emitting display device has the following problems. In the transparent organic light emitting display device that includes a transmissive part and an emissive part, the transmissive part should be formed to maximize a transmittance, and to this end, all elements should be stacked in the emissive part. However, when the TFT layer T is stacked in the emissive part, an auxiliary electrode cannot be stacked in the emissive part, and for this reason, the auxiliary electrode should be stacked separately from the TFT layer T. Two auxiliary electrodes should be vertically stacked for stacking the two auxiliary electrodes in a limited space. Also, since separate masks are used for stacking the two auxiliary electrodes on one layer, the number of masks increases, and for this reason, a manufacturing process becomes complicated. Therefore, a technology to reduce the resistance of the cathode electrode 96 effectively without an increase in number of masks is necessary.